Semiconductor device and method for manufacturing the same

Abstract

A more convenient and highly reliable semiconductor device which has a transistor including an oxide semiconductor with higher impact resistance used for a variety of applications is provided. A semiconductor device has a bottom-gate transistor including a gate electrode layer, a gate insulating layer, and an oxide semiconductor layer over a substrate, an insulating layer over the transistor, and a conductive layer over the insulating layer. The insulating layer covers the oxide semiconductor layer and is in contact with the gate insulating layer. In a channel width direction of the oxide semiconductor layer, end portions of the gate insulating layer and the insulating layer are aligned with each other over the gate electrode layer, and the conductive layer covers a channel formation region of the oxide semiconductor layer and the end portions of the gate insulating layer and the insulating layer and is in contact with the gate electrode layer.

What is claimed is: 
     
       1. A semiconductor device comprising a first transistor comprising a first oxide semiconductor layer, and a second transistor comprising a second oxide semiconductor layer, which are over a substrate, the semiconductor device comprising:
 a first gate electrode layer under the first oxide semiconductor layer with a first gate insulating layer therebetween; 
 a second gate electrode layer under the second oxide semiconductor layer with a second gate insulating layer therebetween; 
 a conductive layer comprising a region overlapping with the first gate electrode layer with the first oxide semiconductor layer therebetween and a region overlapping with the second gate electrode layer with the second oxide semiconductor layer therebetween; 
 a first insulating layer between the first oxide semiconductor layer and the conductive layer in a cross-sectional view; and 
 a second insulating layer between the second oxide semiconductor layer and the conductive layer in the cross-sectional view, 
 wherein the first insulating layer comprises a region covering the first oxide semiconductor layer, and is in contact with the first gate insulating layer, 
 wherein the second insulating layer comprises a region covering the second oxide semiconductor layer, and is in contact with the second gate insulating layer, 
 wherein, in a channel width direction of the first transistor, an end portion of the first gate insulating layer and an end portion of the first insulating layer are aligned with each other, 
 wherein, in a channel width direction of the second transistor, an end portion of the second gate insulating layer and an end portion of the second insulating layer are aligned with each other, 
 wherein, in the channel width direction of the first transistor, each of the first gate electrode layer and the conductive layer extends beyond both edges of the first oxide semiconductor layer, and 
 wherein, in the channel width direction of the second transistor, each of the second gate electrode layer and the conductive layer extends beyond both edges of the second oxide semiconductor layer. 
 
     
     
       2. A semiconductor device comprising a first transistor comprising a first oxide semiconductor layer, and a second transistor comprising a second oxide semiconductor layer, which are over a substrate, the semiconductor device comprising:
 a first gate electrode layer under the first oxide semiconductor layer with a first gate insulating layer therebetween; 
 a second gate electrode layer under the second oxide semiconductor layer with a second gate insulating layer therebetween; and 
 a conductive layer comprising a region overlapping with the first gate electrode layer with the first oxide semiconductor layer therebetween and a region overlapping with the second gate electrode layer with the second oxide semiconductor layer therebetween, 
 wherein, in a channel width direction of the first transistor, each of the first gate electrode layer and the conductive layer extends beyond both edges of the first oxide semiconductor layer, and 
 wherein, in a channel width direction of the second transistor, each of the second gate electrode layer and the conductive layer extends beyond both edges of the second oxide semiconductor layer. 
 
     
     
       3. A semiconductor device comprising a first transistor comprising a first oxide semiconductor layer, and a second transistor comprising a second oxide semiconductor layer, which are over a substrate, the semiconductor device comprising:
 a first gate electrode layer under the first oxide semiconductor layer with a first gate insulating layer therebetween; 
 a second gate electrode layer under the second oxide semiconductor layer with a second gate insulating layer therebetween; and 
 a conductive layer comprising a region overlapping with the first gate electrode layer with the first oxide semiconductor layer therebetween and a region overlapping with the second gate electrode layer with the second oxide semiconductor layer therebetween, 
 wherein, in a channel width direction of the first transistor, each of the first gate electrode layer and the conductive layer extends beyond both edges of the first oxide semiconductor layer, 
 wherein, in a channel width direction of the second transistor, each of the second gate electrode layer and the conductive layer extends beyond both edges of the second oxide semiconductor layer, and 
 wherein, in a plan view, the first transistor is located adjacent to the second transistor in a direction in which the conductive layer extends. 
 
     
     
       4. A semiconductor device comprising a first transistor comprising a first semiconductor layer, and a second transistor comprising a second semiconductor layer, which are over a substrate, the semiconductor device comprising:
 a conductive layer; 
 an insulating layer between the conductive layer and each of the first semiconductor layer and the second semiconductor layer; 
 a source electrode layer electrically connected to the first semiconductor layer and the second semiconductor layer; and 
 a drain electrode layer electrically connected to the first semiconductor layer and the second semiconductor layer, 
 wherein the first semiconductor layer and the second semiconductor layer are arranged in a first direction, 
 wherein the conductive layer extends beyond both side edges of the first semiconductor layer in the first direction, the first direction being the same as a channel width direction of the first transistor, 
 wherein the conductive layer extends beyond the both side edges of the second semiconductor layer in the first direction, the first direction being the same as a channel width direction of the second transistor, 
 wherein one of the source electrode layer and the drain electrode layer extends beyond the both side edges of the first semiconductor layer, 
 wherein the one of the source electrode layer and the drain electrode layer extends beyond the both side edges of the second semiconductor layer, 
 wherein a channel width of the first transistor is larger than a channel length of the first transistor, and 
 wherein a channel width of the second transistor is larger than a channel length of the second transistor. 
 
     
     
       5. The semiconductor device according to  claim 4 , wherein the first direction is a direction in which the semiconductor device is bent. 
     
     
       6. The semiconductor device according to  claim 4 ,
 wherein a pixel portion and a driver circuit portion are provided over the substrate, 
 wherein the pixel portion comprises a light-emitting element, 
 wherein the driver circuit portion comprises the first transistor and the second transistor.